Method and apparatus for beamforming based on broadband antenna

ABSTRACT

A beamforming method based on broadband antenna is provided, comprising: detecting the frequency of input signals of an antenna; determining the effective antenna aperture between elements of the antenna array according to the detected frequency; computing the weight vector of each element of the antenna array to the signals according to the determined effective antenna aperture and the transmission function of the antenna array; multiplying the input signals with said weight vector of each element of the antenna array to the signals, combining them and outputting the beam signals. By performing weighting operation respectively to the input signals after a series of delaying operation, and then combining them, the single digital signals can be acquired. This effectively reduces the odds produced by the antenna between transmitting signals and receiving signals, and thus dramatically improves the communication quality.

FIELD OF THE INVENTION

The present invention relates generally to a beamforming method based onbroadband antenna, and more particularly, to a beamforming methodimplemented in time domain or in frequency domain based on broadbandantenna.

BACKGROUND ART OF THE INVENTION

In common mobile communication environment, signals communicated betweenthe base station and the mobile terminal are transmitted along severalpaths between the receiver and the transmitter. Due to difference inpropagation paths, the same signal may arrive at the receiver viadifferent paths with different propagation delays and DOAs (directionalangle of arrival), thus multi-path interference and signal fading arecaused.

By taking full advantage of the space property of signals, array antennatechniques can reduce multi-path interference and signal deteriorationeffectively, improve system capacity and QoS markedly, and thus won wideapplications in real life.

For the array antenna, beamforming is a basic function. That is, thearray antenna can perform operations like delaying, weighting andcombining to the signals received by the antenna elements, to formantenna beams whose major lobe aims at the direction of the user signalsand null at that of the interference signals, so as to suppress theinterference. Thereby the beams formed by the array antenna havesignificant effect on system performance.

FIG. 1 is a schematic diagram illustrating a one-dimension linear arrayantenna comprising M elements. As shown in FIG. 1, θ is the incidentsignal elevation, d is the space between elements (geometricalaperture), and all elements are assumed to have the same space. Thehalf-power beam width of the array antenna, θ_(0.5), is approximately:

$\begin{matrix}{\theta_{0.5} \approx \frac{50.8 \cdot c}{M \cdot d \cdot f}} & (1)\end{matrix}$wherein M is the number of antenna elements, f is the carrier frequencyof the signals, and c is velocity of light which equals to 3×10⁸ m/s.

The geometrical aperture d, and the number of antenna elements M, aregenerally constant, which means the length of the antenna array, M·d, isconstant too.

As it can be seen from equation (1), if the length of the antenna arrayM·d, is fixed, the antenna can form beams with different width whenreceiving signals with different frequencies. The higher the frequencyis, the narrower the beam width is. Researches indicate that the beamwidth is in inverse ratio to the signal frequency. When broadbandsignals are received not in the direction to which the beam heads, thebeam width of the antenna is relatively narrow for HF (high frequency)signals, so part of HF signals will fall to the null of the antennapattern, thus the energy of these signals will be lost by the beamoutput. Accordingly, the output of the antenna is distorted.

To deal with the above-mentioned problem of antenna output distortion,the present invention provides a beamforming method based on broadbandantenna.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a methodfor beamforming based on broadband antenna In the proposed method, theeffective aperture of the base antenna array is changed according to thesignal frequency, so that the antenna shapes signals with differentfrequency into beams with constant width. On this premise, the weightvector of the antenna for different signal frequency is calculated, andthen the input signals are weighted by the calculated weight vector toequalize the space gain of the antenna for each signal frequency, thusto eliminate distortion of the processed broadband signals.

Another object of the present invention is to provide a method andapparatus for beamforming with constant beam width, for use in mobileterminals with array antenna With this Rx (receiving) method andapparatus, the antenna elements can effectively reduce the odds producedwhen transmitting and receiving signals, thus dramatically improve thecommunication quality.

To achieve the object of the present invention, a method is proposed forbeamforming based on broadband antenna, comprising: measuring thefrequency of the antenna's input signals; determining the effectiveantenna aperture between the elements of the antenna array according tothe measured frequency; computing the weight vector of each antennaelement to the signals according to the determined effective antennaaperture and the transmission function of the antenna array; multiplyingthe input signals with said weight vector of each antenna element to thesignals, combining them and outputting the beam signals.

To achieve the object of the present invention, a method for beamformingbased on broadband antenna is proposed, wherein the step of multiplyingthe input signals with the corresponding weight vectors furtherincludes: performing a series of delaying operations on the inputsignals; multiplying each delayed signal with the corresponding weightvector, and combining each delayed and weighted signal.

To achieve the object of the present invention, a method for beamformingbased on broadband antenna is proposed, further comprising: performingFFT (Fast Fourier Transform) to transform input signals into signals infrequency domain before measuring the frequency of input signals; aftercombining the signals weighted by each element, performing IFFT (InverseFast Fourier Transform) to transform the combined signals in frequencydomain into signals in time domain.

To achieve the object of the present invention, a beamforming apparatusbased on broadband antenna is proposed, comprising: an effective antennaaperture computing module, for measuring the frequency of input signalsof the antenna, and then determining the effective antenna aperturebetween elements of the antenna array according to the measuredfrequency; a weight vector computing module, for computing the weightvector of each element to the input signals according to the determinedeffective antenna aperture and the transmission function of the antennaarray; a beam generating module, for multiplying the input signals withthe weight vector of each said antenna element to the input signals, andthen combining them and outputting the beam signals.

To achieve the object of the present invention, a beamforming apparatusbased on broadband antenna is proposed, wherein the beam generatingmodule further includes: a plurality of groups of delayers, each groupfor performing a series of delaying operations on the input signals; aplurality of groups of weight vector adjusting modules, each group formultiplying each delayed signal with said corresponding weight vector; abeam combining module, for combining the weighted signals, andoutputting the combined signals.

To achieve the object of the present invention, a beamforming apparatusbased on broadband antenna is proposed, further comprising: atime/frequency transforming module, for performing FFT (Fast FourierTransform) to the input signals of the antenna, so as to provide thetranstormed signals in frequency domain to said effective antennaaperture computing module; a frequency/time transforming module, forperforming IFFT (Inverse Fast Fourier Transform) to the beam signals infrequency domain outputted from said beam generating module, to obtainbeam signals in time domain.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a schematic diagram illustrating an existing discrete linearantenna array;

FIG. 2 is a schematic diagram illustrating space re-sampling inaccordance with the present invention;

FIG. 3 is a block diagram illustrating a beamforming module based onbroadband antenna in accordance with the present invention;

FIG. 4 is a block diagram illustrating a Tx beamforming apparatus basedon broadband antenna and implemented in time domain in accordance withthe present invention.

FIG. 5 is a block diagram illustrating a Tx beamforming apparatus basedon broadband antenna and implemented in frequency domain in accordancewith the present invention.

FIG. 6 is a block diagram illustrating an Rx beamforming apparatus basedon broadband antenna and implemented in time domain in accordance withthe present invention.

FIG. 7 is a block diagram illustrating an Rx beamforming apparatus basedon broadband antenna and implemented in frequency domain in accordancewith the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in equation (1), antenna beams with different width can beacquired by changing the geometrical aperture d of the antenna; forsignals with different frequency f; beams with constant width can beacquired by changing the geometrical aperture d to keep the half-powerbeam width θ_(0.5) unchanged.

The beamforming method proposed in the present invention is based on theabove-mentioned principle. The antenna can shape beams with constantwidth for different signal frequency, by changing the effective aperturefor different signal frequency. On this premise, the weight vector ofthe antenna array for different signal frequency is calculated, and theninput signals are weighted with the calculated weight vector so that thespace gain of the antenna for each signal frequency can be equalized.

In the following, a detailed description will be given to the procedurefor beamforming method, by taking the continuous antenna array as anexample.

First, when the frequency of the signals inputted to the antenna elementchanges from original frequency f₀ to frequency f_(j), the continuousantenna array should be re-sampled at the antenna element to ensure thatits effective aperture changes from d=λ₀/2 to d′=λ_(j)/2, thus to keepthe width of the antenna beam constant with the two frequencies. FIG. 2is a schematic diagram for illustrating space re-sampling, wherein d isthe effective aperture of element 2 corresponding to original frequencyf₀, and d′ is the effective aperture of the re-sampled element 2′corresponding to frequency f₁.

Second, just as a discrete antenna array may be taken as a digitalfilter, a continuous antenna array can be taken as an analog filter. Itstransmission function can be represented in Equation (2):

$\begin{matrix}{{h_{a}(x)} = {\sum\limits_{i = 1}^{M}\left\lbrack {{w_{0}(i)} \cdot \frac{\sin\left( {{\pi\left( {x - {\left( {i - 1} \right)\frac{\lambda_{j}}{2}}} \right)}/\frac{\lambda_{j}}{2}} \right)}{\pi\left( {x - {\left( {i - 1} \right)\frac{\lambda_{j}}{2}}} \right)}} \right\rbrack}} & (2)\end{matrix}$where w₀(i) is the weight value corresponding to original frequency f₀,λ_(j) the wave length corresponding to frequency f_(j), and x thedistance to the first antenna element (reference point). As shown inthis transmission function, the effect of each antenna element on inputsignals is relevant to weight vector w₀(i) corresponding to the originalfrequency f₀, the distance to the first antenna array element x, and thewave length of the input signals.

Third, the weight vector of each antenna element corresponding tofrequency f₁ is computed according to the effective aperture of the newantenna element 2′ and the transmission function of the continuousantenna array. Calculation of the weight vector is given in Equation(3):

$\begin{matrix}{{{w_{j}(m)} \approx {\frac{f_{j}}{f_{0}}{\sum\limits_{i = 1}^{M}\left\lbrack {{w_{0}(i)} \cdot \frac{\sin\left\{ {\pi\left\lbrack {{\frac{f_{j}}{f_{0}}\left( {m - 1} \right)} - \left( {i - 1} \right)} \right\rbrack} \right\}}{\pi\left\lbrack {{\frac{f_{j}}{f_{0}}\left( {m - 1} \right)} - \left( {i - 1} \right)} \right\rbrack}} \right\rbrack}}}\mspace{20mu}{{m = 1},2,{\ldots\mspace{11mu} M},{i \neq m}}} & (3)\end{matrix}$

Last, the input signals are multiplied with the weight vector computedas above and combined and outputted through a combiner to generate beamswith constant width.

FIG. 3 is a block diagram illustrating a beamforming apparatus based onbroadband antenna, comprising: an effective antenna aperture computingmodule 10, for measuring the frequency of input signals X(t) of theantenna and then determining the effective antenna aperture between theelements according to the measured frequency; a weight vector computingmodule 20, for computing the weight vector of each antenna element tothe signals according to the determined effective antenna aperture andtransmission function of the antenna array; a beam generating module 30,for multiplying the input signals X(t) with the weight vector of eachsaid antenna element, combining them and outputting the beam signalsY(t).

The effective antenna aperture computing module 10, weight vectorcomputing module 20 and beam generating module 30 as described above,can be implemented in either computer software or hardware.

In the following, descriptions will be given respectively to how theabove beamforming method and apparatus is applied in time domain andfrequency domain based on broadband antenna, by exemplifying the receiptand transmission of signals.

FIG. 4 illustrates the Tx beamforming apparatus based on broadbandantenna implemented in time domain, comprising: an effective antennaaperture computing module 10; a weight vector computing module 20; abeam generating module 30.

As shown in FIG. 4, first the effective antenna aperture computingmodule 10 measures the frequency of each signal to be transmitted intime domain, and determines the effective antenna aperture between theelements of the antenna array as d=λ_(j)/2 according to the measuredfrequency; then the weight vector computing module 20 computes theweight vector of each antenna element to the signals according to thedetermined effective antenna aperture; last, the beam generating module30 multiplies each signal in time domain with the computed weightvector, combines them and outputs the multi-beam signals with constantwidth, (Y₁ . . . Y_(m) . . . Y_(M)).

FIG. 5 depicts a Tx beamforming apparatus based on broadband antenna andimplemented in frequency domain, comprising: effective antenna aperturecomputing module 10, weight vector computing module 20, beam generatingmodule 30, FFT module 40 and IFFT module 50.

As shown in FIG. 5, the FFT module 40 first transforms each signal intime domain to be transmitted into signal in frequency domain. Then, theeffective antenna aperture computing module 10 measures the frequency ofeach transformed signal in frequency domain and determines the effectiveantenna aperture between the elements of the antenna array as d=λ_(j)/2according to the measured frequency. The weight vector computing module20 computes weight vector or each antenna element according to thedetermined effective antenna aperture. Afterwards, the beam generatingmodule 30 multiplies each signal in frequency domain with the computedweight vector, to output the multi-channel beam signals with constantwidth in frequency domain. Last, IFFT module 50 transforms each channelof beam signal into signal in time domain (Y₁ . . . Y_(m) . . . Y_(M)).

FIG. 6 illustrates an Rx beamforming apparatus based on broadbandantenna implemented in time domain, comprising: effective antennaaperture computing module 10, weight vector computing module 20 and beamgenerating module 30 composed of a plurality of groups of delayers 60, aplurality of groups of weight adjusting modules 70 and a beam combiningmodule 80.

As shown in FIG. 6, the effective antenna aperture computing module 10measures the frequency of signal (X₁ . . . X_(m) . . . X_(M)) in timedomain received by each antenna element, and determines the effectiveantenna aperture between the elements of the antenna array as d=λ_(j)/2according to the measured frequency; then the weight vector computingmodule 20 computes the weight vector of each antenna element accordingto the determined effective antenna aperture; the plurality of groups ofdelayers 60 perform a series of delaying operations on each receivedsignal in time domain; the plurality of groups of weight adjustingmodules 70 weight each delayed signal in time domain with thecorresponding weight vector computed by weight vector computing module70; last, the beam combining module 80 combines each weighted signals intime domain and outputs the combined beam signals with constant width.

Detailed description will be given below to how this apparatus works:

1. Computation of the Effective Antenna Aperture and the Weight Vector

First, the effective antenna aperture computing module 10 measures thefrequency of input baseband signals, and determines the effectiveantenna aperture between the elements of the antenna array as d=λ_(j)/2according to the measured frequency. Then, the weight vector computingmodule 20 computes the weight vector according to the determinedeffective antenna aperture. Specifically as:

(1) If the broadband signal is known waveform, its spectrum range isalso known, then its pulse response in an element of the base array ish′(n); if the broadband signal is unknown, its pulse response in anelement of the base array, h′(n), is to be determined by estimating itsspectrum range with FFT and time/frequency analysis.

(2) When the odds caused by the elements' receiving broadband signal areeliminated, the weight coefficient h_(mn) (or denoted as h_(m)(n))should satisfy equation (4) (without considering the channel effect):y(t)=x(t)=x(t)

h′(n)

h _(m)(n)  (4)where

denotes convolution in time domain.

(3) Compute the weight coefficient with equation (4) to obtain h_(•n) =h_(mn)(m=1, . . . , M), where h_(•n) denotes the weight coefficient ofone element in time domain and is relevant to the effective antennaaperture.

(4) Determine the weight coefficients h_(m•) to acquire the scheduledbeam shape through weighting like Chebyshev or Butterworth, whereinh_(m•) denotes the weight coefficients of all elements at the same time.

(5) Determine the weight coefficient h_(mn) with h_(m•) and h_(•n):h _(mn) =h _(•n) ×h _(m•)  (5)

(6) Supply each generated weight coefficient h_(mn) to each group ofweight adjusting modules 70.

2. Weighting

As shown in FIG. 6, the input signals are delayedτ_(m)=(m−1)·d/c·sin(α₀), wherein τ_(m) is the delay relative to thereference point, for forming beams with typical viewing angle as α₀ andT_(s) is a delaying unit. Each signal that has been performed a seriesof delaying operations, is multiplied with each weight coefficientsupplied by the weight vector computing module 20 to get two-dimensiontime-space processed multi-beam signals.

3. Combining

Each channel of weighted signal is combined in the beam combining module80, to get the single-channel digital signal with constant beam width.

FIG. 7 charts an Rx beamforming apparatus based on broadband antennaimplemented in frequency domain, where x_(m)(t) is the mth channel ofinput signal in time domain, X_(Bk)(f) the output of the kth beam withdirectional angle α_(k) in frequency domain, x_(Bk)(t) the eventualoutput in time domain, K the number of the formed beams, andB_(mk)(f_(j)) the transform matrix. It can be represented in Equation(6):

$\begin{matrix}{{B\left( f_{j} \right)} = {W_{j}\left( {W_{j}^{H}W_{j}} \right)}^{\frac{1}{2}}} & (6)\end{matrix}$where W_(j)=[w_(j1), w_(j2) . . . w_(jk) . . . w_(jK)] and w_(jk) is theweight vector of the kth beam. Through computing with Equation (3),w_(jk) can be expressed as in Equation (7):

$\begin{matrix}\begin{matrix}{w_{jk} = {{diag}\left\lbrack {1,{{\mathbb{e}}^{{- {j2\pi}}\;{f_{j}{({d/c})}}{\sin{(\alpha_{k})}}}\mspace{11mu}\ldots\mspace{11mu}{\mathbb{e}}^{{- {j2\pi}}\;{f_{j}{({d/c})}}{\sin{(\alpha_{k})}}{({m - 1})}}\mspace{11mu}\ldots}}\mspace{11mu} \right.}} \\{\left. {\mathbb{e}}^{{- {j2\pi}}\;{f_{j}{({d/c})}}\;{\sin{(\alpha_{k})}}{({M - 1})}} \right\rbrack \times w_{j0}} \\{= {{{diag}\left( {\partial\left( {f_{j},\alpha_{k}} \right)} \right)} \times w_{j0}}}\end{matrix} & (7)\end{matrix}$

As shown in FIG. 7, first, the input signal in time domain x_(m)(t) isFFT transformed into signal in frequency domain. Second, the effectiveantenna aperture computing module 10 measures the frequency of thesignal in frequency domain and determines the effective antenna aperturebetween the elements of the antenna array as d=λ_(j)/2 according to themeasured frequency. Third, the weight vector computing module 20computes the weight vector of each antenna element to the signalaccording to the determined effective antenna aperture and transmissionfunction of the antenna array, and provides the computed weightcoefficients to the transform matrix of each channel. Fourth, eachchannel of signal in frequency domain is weighted with the transformmatrix of the corresponding channel, and combined by a plurality ofsignal combiners to generate multi-beam signals in frequency domain.Last, the beam signals in frequency domain are transformed into beamsignals in time domain through IFFT.

Beneficial Results of the Invention

As described above, when the frequency of the signals inputted to theantenna element changes from original frequency f₀ to frequency f_(j),the antenna array should be re-sampled at the antenna element to ensurethat its effective aperture changes from d=λ₀/2 to d′=λ_(j)/2, thus tokeep the width of the antenna beam constant with the two frequencies.The weight vector corresponding to frequency f₁ can be computedaccording to the effective antenna aperture of the new antenna array andthe transmission function of the continuous antenna array. Output ofbeams with constant width can be obtained by multiplying the inputsignals with the weight vector, thus the distortion of the processedbroadband signals is eliminated.

Moreover, when the above method and apparatus for beamforming withconstant width are applied in mobile terminals with array antennas,through respectively weighting the input signals which have beenperformed on a series of delaying operations and combining thetwo-dimension time-space processed signals to obtain single-channeldigital signals, the warp produced by the antenna array elements whentransmitting and receiving signals, can be effectively reduced, thus toimprove the communication quality dramatically.

It's to be understood by those skilled in the art that the beamformingmethod and apparatus as proposed in the present invention is applicableto broadband wireless transceiving systems, base stations and mobileterminals of next generation (3G and 4G) communication system, chipsetsand components for use in array antennas and broadband antennas.

Furthermore, it's to be understood by those skilled in the art that thebeamforming method and apparatus as proposed in the present inventioncan be modified considerably without departing from the spirit and scopeof the invention as defined by the appended claims.

1. A beam shaping method based on broadband antenna, comprising:measuring a frequency of input signals of an antenna, the antennacomprising an antenna array, wherein the input signals can includesignals with different frequencies, including an original frequency anda second frequency different from the original frequency; determining aneffective antenna aperture between elements of the antenna arrayaccording to a measured frequency, wherein determining includesre-sampling at the antenna elements to ensure that the antenna'seffective aperture changes from a first effective aperture to a secondeffective aperture to keep a beam width of the antenna constant with thetwo frequencies; computing a weight vector of each element of theantenna array to the input signals according to (i) the determinedeffective antenna aperture and (ii) a transmission function of theantenna array; and multiplying each of the input signals with acorresponding one of said weight vector of each element of the antennaarray to the input signals, combining them into beam signals withconstant beam width and outputting the beam signals.
 2. The beam shapingmethod based on broadband antenna according to claim 1, wherein saidstep of multiplying the input signals with the corresponding weightvectors further includes: performing a series of delaying operations onthe input signals; multiplying each delayed signal with thecorresponding weight vector, and combining each delayed weighted signal.3. The beam shaping method based on broadband antenna according to claim1, further comprising: performing FFT (Fast Fourier Transform) first soas to transform input signals into signals in frequency domain beforemeasuring the frequency of input signals, and performing IFFT (InverseFast Fourier Transform) so as to transform the combined signals infrequency domain into signals in time domain after combining the signalsweighted by each element of the antenna array.
 4. The beam shapingmethod based on broadband antenna according to claim 1, wherein saideffective antenna aperture between elements is d=λ/2, wherein λ is thewavelength of said input signals.
 5. The beam shaping method based onbroadband antenna according to claim 1, is performed by at least one ofthe base station and the mobile terminal.
 6. A beam shaping apparatusbased on broadband antenna, comprising: an effective antenna aperturecomputing module, for measuring a frequency of input signals of anantenna, the antenna comprising an antenna array, wherein the inputsignals can include signals with different frequencies, including anoriginal frequency and a second frequency different from the originalfrequency, and then determining an effective antenna aperture betweenelements of the antenna array according to a measured frequency, whereindetermining includes re-sampling at the antenna elements to ensure thatthe antenna's effective aperture changes from a first effective apertureto a second effective aperture to keep a beam width of the antennaconstant with the two frequencies; a weight vector computing module, forcomputing the a weight vector of each element of the antenna array tosaid input signals according to (i) the determined effective antennaaperture and (ii) a transmission function of the antenna array; and abeam generating module, for multiplying each of said input signals witha corresponding one of said weight vector of each element of the antennaarray to said input signals, and then combining them into beam signalswith constant beam width and outputting the beam signals.
 7. The beamshaping apparatus based on broadband antenna according to claim 6,wherein said beam generating module further includes: a plurality ofgroups of delayers, each group for performing a series of delayingoperations on the input signals; a plurality of groups of weight vectoradjusting modules, each group for multiplying each delayed signal withsaid corresponding weight vector; and a beam combining module, forcombining the weighted signals, and outputting the combined signals. 8.The beam shaping apparatus based on broadband antenna according to claim6, further comprising: a time/frequency transforming module, forperforming FFT (Fast Fourier Transform) to the input signals of theantenna, so as to provide the transformed signals in frequency domain tosaid effective antenna aperture computing module; and a frequency/timetransforming module, for performing IFFT (Inverse Fast FourierTransform) to the beam signals in frequency domain outputted from saidbeam generating module, to acquire the beam signals in time domain. 9.The beam shaping equipment based on broadband antenna according to claim6, wherein said effective antenna aperture between elements of theantenna array is d=λ/2, where λ is the wavelength of said input signals.10. A base station system, comprising: a radio signal transceivingmodule, for receiving or transmitting radio signals; an effectiveantenna aperture computing module, for measuring a frequency of inputsignals of an antenna of the base station, the antenna comprising anantenna array, wherein the input signals can include signals withdifferent frequencies, including an original frequency and a secondfrequency different from the original frequency, and then determining aneffective antenna aperture between elements of the antenna array of thebase station according to a measured frequency, wherein determiningincludes re-sampling at the antenna elements to ensure that theantenna's effective aperture changes from a first effective aperture toa second effective aperture to keep a beam width of the antenna constantwith the two frequencies; a weight vector computing module, forcomputing a weight vector of each element of the antenna array of thebase station to said input signals according to (i) the determinedeffective antenna aperture and (ii) a transmission function of theantenna array; and a beam generating module, for multiplying each ofsaid input signals with a corresponding one of the weight vector of eachelement of the antenna array of the base station to said input signals,then combining them into beam signals with constant beam width andoutputting the beam signals.
 11. The base station system according toclaim 10, wherein said beam generating module further includes: aplurality of groups of delayers, each group for performing a series ofdelaying operations on the input signals; a plurality of groups ofweight adjusting modules, each group for multiplying each delayed signalwith said corresponding weight vector; and a beam combining module, forcombining said weighted signals and outputting the combined signals. 12.The base station system according to claim 10, further comprising: atime/frequency transforming module, for performing FFT (Fast FourierTransform) to input signals of the antenna of the base station, so as toprovide signals in frequency domain to said effective antenna aperturecomputing module; and a frequency/time transforming module, forperforming IFFT (Inverse Fast Fourier Transform) to the beam signals infrequency domain combined and outputted from said beam generatingmodule, so as to acquire the beam signals in time domain.
 13. The basestation system according to claim 10, wherein said effective antennaaperture between elements of antenna array is d=λ/2, where λ is thewavelength of said input signals.
 14. A mobile terminal, comprising: aradio signal transceiving module, for receiving or transmitting radiosignals; an effective antenna aperture computing module, for measuring afrequency of input signals of an antenna of the mobile terminal, theantenna comprising an antenna array, wherein the input signals caninclude signals with different frequencies, including an originalfrequency and a second frequency different from the original frequency,and then determining an effective antenna aperture between elements ofthe antenna array of the mobile terminal according to a measuredfrequency, wherein determining includes re-sampling at the antennaelements to ensure that the antenna's effective aperture changes from afirst effective aperture to a second effective aperture to keep a beamwidth of the antenna constant with the two frequencies; a weight vectorcomputing module, for computing a weight vector of each element of theantenna array of the mobile terminal to said input signals according to(i) the determined effective antenna aperture and (ii) a transmissionfunction of the antenna array; and a beam generating module, formultiplying each of said input signals with a corresponding one of theweight vector of each element of the antenna array of the mobileterminal to said input signals, then combining them into beam signalswith constant beam width and outputting the beam signals.
 15. The mobileterminal according to claim 14, wherein said beam generating modulefurther includes: a plurality of groups of delayers, each for performinga series of delaying operations on the input signals; a plurality ofgroups weight adjusting modules, each group for multiplying each delayedsignal with said corresponding weight vector; and a beam combiningmodule, for combining said weighted signals and outputting the combinedsignals.
 16. The mobile terminal according to claim 14, furthercomprising: a time/frequency transforming module, for performing FFT(Fast Fourier Transform) to the input signals of the antenna of saidmobile terminal, so as to provide the transformed signals in frequencydomain to said effective antenna aperture computing module; and afrequency/time transforming module, for performing IFFT (Inverse FastFourier Transform) to the beam signals in frequency domain combined andoutputted from said beam generating module, so as to acquire beamsignals in time domain.
 17. The mobile terminal according to claim 14,wherein said effective antenna aperture between elements of the antennaarray is d=λ/2, where λ is the wavelength of said input signals.